What is Leptin?

Most of us have heard of the hormone insulin, the glycemic index and how sugar affects the chemistry of your body. Insulin's primary job is to keep blood sugar levels stable by transporting sugar calories to the muscle cells to be used as energy or to the liver to be stored as short term energy in the form of glycogen. If those muscle cells are not being used, or already have enough fuel in them, and the liver is always full (from eating too often), those calories go directly to fat storage.
Most of us also know about insulin resistance - where the body produces more than enough insulin, but the cells become insensitive to it, essentially rejecting the excess fuel that insulin is constantly bringing, making insulin essentially nonfunctional.

Leptin is a primary hormone that is secreted by fat cells, that works as one of the master hormones in the body - working with insulin and other hormones to govern metabolism. When your brain receives a signal that leptin levels are ok, then the body knows it does not need to store extra fat and so reduces appetite and speeds up metabolism. When leptin levels fall, the brain thinks there is not enough fuel stored, and tells your body to store more fat and slow down metabolism. Just as one can produce excess insulin and become insulin resistant, one can also become leptin resistant - where one's fat cells are making tons of leptin, but the brain is resistant to the signal. Most overweight people make plenty of leptin - the brain is just unable to sense the message, and continues to send the message to store fat and slow metabolism.

Fat cells are known to secrete other communication signals in addition to leptin that affect almost every other system in the body - liver, reproductive, kidney, cardiovascular, thyroid and adrenal function. They are collectively one of the organs of the body. Low leptin levels are also implicated in loss of bone density when the signal is not working properly.

Leptin and insulin work together - insulin stimulates leptin production, and higher leptin levels can turn off insulin production. In leptin resistance, the pancreatic cells that produce insulin also become leptin resistant, and the insulin response is unregulated, and consequently, the leptin production becomes unregulated. Unregulated insulin brings on insulin resistance - and so it is a vicious cycle. High cholesterol can also be due to leptin resistance - the liver does not receive the proper signal, and does not shut off cholesterol production. The body makes 90% of the cholesterol present in the blood. Only a small percentage come from the diet. Leptin and insulin resistance occur together.

According to Byron J. Richards book 'Mastering Leptin' (a great book, btw), he proposes 5 eating rules to balance leptin, and consequently insulin. He goes into great depth for the biochemical reasons for these rules in his book.

1. Do not eat after dinner. Make sure there are 11 or 12 hours between dinner and breakfast with only water in between.
2. Eat three meals a day with 5-6 hours in between meals. No snacking.
3. Eat slowly and do not eat large meals
4. Eat a high protein breakfast
5. Reduce the amount of carbohydrates eaten. In my experience, this means no refined sugar, refined flour, and making most of the carbohydrates you eat primarily vegetables, and whole grains.